Non-friction braking system?

Calab wrote:
> I remember seeing on TV a while ago that there was someone trying to
> beat a land speed record. I really don't remember very many details of
> the show, but one thing I do remember is that they needed some way of
> stopping the vehicle very well, without locking up the wheels.
>
> The solution involved an aluminum "disc" on the axle that caused drag
> the closer it was moved to a coppper(???) "disc" on th wheel. As long as
> the vehicle was moving, the two discs could not be pressed into making
> contact. The more force used to press the discs together, the stronger
> the braking power was.
>
> This sounds like the ultimate permanent ABS brake system. No wearing out
> of friction materials, the very simplest of ABS implementation, etc.
>
> I can't find anything online about this kind of braking system, or the
> physics behind it. I don't have enough details to do a decent Google
> search. I'm hoping someone here recognizes what I'm talking about and ca
> give more information.
>
> Does anyone know what I'm talking about here?
>


Sounds like an eddy current braking system.

--
Steve W.
Near Cooperstown, New York

On May 20, 10:00 pm, "Steve W." <[email protected]> wrote:
> Calab wrote:
> > I remember seeing on TV a while ago that there was someone trying to
> > beat a land speed record. I really don't remember very many details of
> > the show, but one thing I do remember is that they needed some way of
> > stopping the vehicle very well, without locking up the wheels.
>
> > The solution involved an aluminum "disc" on the axle that caused drag
> > the closer it was moved to a coppper(???) "disc" on th wheel. As long as
> > the vehicle was moving, the two discs could not be pressed into making
> > contact. The more force used to press the discs together, the stronger
> > the braking power was.
>
> > This sounds like the ultimate permanent ABS brake system. No wearing out
> > of friction materials, the very simplest of ABS implementation, etc.
>
> > I can't find anything online about this kind of braking system, or the
> > physics behind it. I don't have enough details to do a decent Google
> > search. I'm hoping someone here recognizes what I'm talking about and ca
> > give more information.
>
> > Does anyone know what I'm talking about here?
>
> Sounds like an eddy current braking system.
>
> --
> Steve W.
> Near Cooperstown, New York

True. However, eddy current brakes need another auxillary brake like
a friction brake, or say the eddy current brake is the aux brake. The
problem with eddy current brakes is that they only work with
considerable motion. The braking falls to very low values at low
speeds so you still need a brake to "park" it where you want to stop
it.

Steve W. wrote:
> Calab wrote:
>> I remember seeing on TV a while ago that there was someone trying to
>> beat a land speed record. I really don't remember very many details of
>> the show, but one thing I do remember is that they needed some way of
>> stopping the vehicle very well, without locking up the wheels.
>>
>> The solution involved an aluminum "disc" on the axle that caused drag
>> the closer it was moved to a coppper(???) "disc" on th wheel. As long
>> as the vehicle was moving, the two discs could not be pressed into
>> making contact. The more force used to press the discs together, the
>> stronger the braking power was.
>>
>> This sounds like the ultimate permanent ABS brake system. No wearing
>> out of friction materials, the very simplest of ABS implementation, etc.
>>
>> I can't find anything online about this kind of braking system, or the
>> physics behind it. I don't have enough details to do a decent Google
>> search. I'm hoping someone here recognizes what I'm talking about and
>> ca give more information.
>>
>> Does anyone know what I'm talking about here?
>>
>
>
> Sounds like an eddy current braking system.
>

Yes, but without a magnet in there, aint gonna be no eddy currents. I
don't think the OP is really remembering enough details.

The other problem with all electromagnetic braking systems is that their
effectiveness decreases as speed approaches zero, so its hard to use
them to come to a complete and total stop. For example, diesel-electric
locomotives use dynamic braking (operating the traction motors as
generators and dumping the electricity to a resistor grid cooled by a
big fan) to slow down or regulate speed on long downgrades, but to come
to a complete stop they have to use the friction brakes at some point.

In article <[email protected]>,
Steve <[email protected]> wrote:

> Steve W. wrote:
> > Calab wrote:
> >> I remember seeing on TV a while ago that there was someone trying to
> >> beat a land speed record. I really don't remember very many details of
> >> the show, but one thing I do remember is that they needed some way of
> >> stopping the vehicle very well, without locking up the wheels.
> >>
> >> The solution involved an aluminum "disc" on the axle that caused drag
> >> the closer it was moved to a coppper(???) "disc" on th wheel. As long
> >> as the vehicle was moving, the two discs could not be pressed into
> >> making contact. The more force used to press the discs together, the
> >> stronger the braking power was.
> >>
> >> This sounds like the ultimate permanent ABS brake system. No wearing
> >> out of friction materials, the very simplest of ABS implementation, etc.
> >>
> >> I can't find anything online about this kind of braking system, or the
> >> physics behind it. I don't have enough details to do a decent Google
> >> search. I'm hoping someone here recognizes what I'm talking about and
> >> ca give more information.
> >>
> >> Does anyone know what I'm talking about here?
> >>
> >
> >
> > Sounds like an eddy current braking system.
> >
>
> Yes, but without a magnet in there, aint gonna be no eddy currents. I
> don't think the OP is really remembering enough details.
>
> The other problem with all electromagnetic braking systems is that their
> effectiveness decreases as speed approaches zero, so its hard to use
> them to come to a complete and total stop. For example, diesel-electric
> locomotives use dynamic braking (operating the traction motors as
> generators and dumping the electricity to a resistor grid cooled by a
> big fan) to slow down or regulate speed on long downgrades, but to come
> to a complete stop they have to use the friction brakes at some point.

Considering the application the OP originally saw it connected with, I'd
say that's one of those "no big deal" things. I'd be betting on the
system being intended to slow the beast down to "conventional speeds"
without locking (or even grabbing real hard for an instant) a wheel at
some ridiculous speed, thus causing the whole thing to go every which
way but loose. Once the thing is down to a reasonable speed,
conventional brakes can take over without anywhere near as much concern
for whether they lock or grab.

As in, a brake locking or grabbing at 500+ MPH is likely to result in a
TOTAL disaster, but locking/grabbing at lower speeds (for grins, let's
say 30 MPH or below) is likely going to be mildly annoying, perhaps
cause some (relatively) insignificant loss of control, or maybe even do
a little damage, but in comparison to the potential consequences of the
same lock/grab happening at 500+ MPH, it will effectively be a non-event.

--
Don Bruder - [email protected] - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info

On Wed, 21 May 2008 10:16:14 -0500, Steve <[email protected]> wrote:

.
>
>The other problem with all electromagnetic braking systems is that their
>effectiveness decreases as speed approaches zero, so its hard to use
>them to come to a complete and total stop. For example, diesel-electric
>locomotives use dynamic braking (operating the traction motors as
>generators and dumping the electricity to a resistor grid cooled by a
>big fan) to slow down or regulate speed on long downgrades, but to come
>to a complete stop they have to use the friction brakes at some point.


So do other braking systems like jet aircraft. Jets are diverted to
slow the plane down and then friction brakes assist the end stages of
stopping and steering.

However, any system which uses less energy than friction is a step or
stride in the right direction.